1. Field of the Invention
The present invention relates to a manufacturing method of semiconductor devices, and especially relates to a gap fill treatment for via process.
2. Description of Related Art
In today's booming development of integrated circuits, scaling down and integration of the device are inevitable trend and also are important problems on which the industry is actively working. In the entire semiconductor manufacturing process, the key which affects the size of the device is the technology of the photolithography process. Also, along with high integration of the semiconductor device, the critical dimension (CD) of the integrated circuit is getting smaller, and thus the resolution required for the photolithography process is getting higher.
During the semiconductor manufacturing process, it is often required to perform gap fill treatment to various openings. Various deposition methods to fill various materials and form a gap-filling material layer are used for the openings which are formed during the semiconductor manufacturing process. For example: an insulation material is filled in trenches of the Shallow Trench Isolation (STI) structure; a conductive layer is filled in contact holes of the Inter-Layer Dielectric (ILD) structure; a conductive layer is filled in via openings of the Inter-Metal Dielectric (IMD) structure; or a conductive layer is filled in dual damascene openings of the metal interconnect structure.
However, during the gap fill treatment, if the difference in the pattern density between the dense pattern region and the isolated pattern region is great, it may cause difference in thickness of the photoresist layer between these regions and thus cause the step height. The difference in the step height may cause the gap-filling material layer to have difference in thickness and an uneven surface, which causes de-focus in the subsequent exposure process and causes etching to be uneven, thereby affect the resolution of the photolithography process.
Therefore, well known gap fill treatment methods may use the etching back method for flattening the surface so as to allow a bottom anti-reflective layer or other material layers which are subsequently formed on the surface of the substrate and the openings to preserve favorable flatness. However, the etching back methods cannot treat the difference in thickness (i.e. the difference in step height) of the gap-filling material layer of each opening resulted from the pattern densities. The etching back methods also have a problem that the gap-filling material layer may be easily eroded by the solvent used in the subsequent process so that the difference in thickness of the gap-filling material layer filled in the openings and unevenness of the pattern surface cannot be solved.